Method of effecting the solidification of metals under gaseous pressure



HMEYER 3,279,005 E SOLIDIFICATION OF METALS OUS PRESSURE 5 Sheets-Sheet l Oct.` 18, 1966 w, WE

METHOD 0F EFFECTING TH UNDER GASE F-led Sept. 2, 1964 27 2// aq/ 32m] i V Oct. 18, 1966 w. WEHMEYER 3,279,005

METHOD OF EFFECTING THE SOLIDIFICATION OF METALS UNDER GSEOUS PRESSURE Filed Sept. 2, 1964 5 Sheets-Sheet 2 Oct. 18, 1966 w. wEHMEYER 3,279,005

METHOD OF EFFECTING THE SOLIDIFICATION OF METALS UNDER GASEOUS PRESSURE Y 5 Sheets-Sheet 5 Filed Sept. 2, 1964 Oct. 18, 1966 w. wl-:HMEYER 3,279,005

METHOD OF EFFECTING THE SOLIDIFICATION OF METALS UNDER GASEOUS PRESSURE F'iled Sept. 2, 1964 l 5 Sheets-Sheet 4 Oct. 18, 1966 w. wEHMl-:YER 3,279,005

METHOD OF EFFECTING THE SOLIDIFICATION OF METALS UNDER GASEOUS PRESSURE 5 Sheets-Sheet 5 Filed Sept. 2, 1964 o o, r s

United States Patent O 3,279,005 METHD F EFFECTING THE SOLIDIFICATION 0F METALS UNDER GASEOUS PRESSURE Werner Wehmeyer, Essen, Germany, assignor to Schloemann Aktiengesellschaft, Dusseldorf, Germany Filed Sept. 2, 1964, Ser. No. 393,931 Claims priority, application Germany, Sept. 10, 1963,

Sch 33,847 3 Claims. (Cl. 22`200) It is known that metal, when it is cast and more or less rapidly solidified, acquires, owing to the shrinkage process upon cooling, cavities which can no longer be lled up by sucking in metal, kept as uid as possible right to the end of the solidication process, from the rises or the lost heads.

It is likewise known that these contraction cavities, also known as shrink holes, can be obviated if the met-al, in a liquid or semi-solidiiied condition, is subjected to pressure, and is kept under a constant pressure until the moment of complete solidifcation, as described in German patent specification No. 159,118, of February 18, 1903. In the process set forth in that speciiication, a constant low pressure is passed by way of a tube, from a pressure-gas storage, into the chill-mould lled with metal and closed, and this pressure connection is maintained during the solidication process.

Furthermore, by publication in Stahl und Eisen, 81 (August 17, 1961), 17, page 1146/48, a process is known in which steel, in a semi-solidified condition, is kept in moulds, which are cooled with water, on hydraulic presses, by the upper part of the mould, under a constant pressure of from 6 to 10 kilogrammes per square millimetre, until the solidication of the steel is completed. The steel casting thus obtained is free from shrink holes and gas bubbles, has a very dense or compact texture, and higher tensile strength, elastic limit, extension and notch impact strength than rolled material of the same analysis. Whilst the iirst-mentioned process works only with a low pressure, which is too small to yield any improvement of texture, the pressures employed with this second process are sufficient to improve the texture.

This latter process has however the disadvantage that a large number of presses and cooled moulds have to be set up if a large number of castings, say from 60 to 120 castings per hour, are to be produced. The number of presses and chill-moulds increases moreover with the Wall thickness, the cross-sectional area and the weight of the castings, because these factors determine the solidification time. The expenditure for so many presses influences the economy of the process.

It is the object of the present invention, with the same number of cooled moulds that is required for a high output, but with a set of only from two to tive relatively small presses, to ensure the economy of a process which delivers finished castings that are solidified under a high and constant pressure.

For this purpose the invention starts from the process mentioned at the outset for obtaining the solidication of metals under gaseous pressure.

The process according to the invention consists in obtaining the desired gaseous pressure within the casting mould by the rise of pressure of an inert gas forced into the closed mould under a high pressure, owing to it being heated by the heat contained in the liquid or semi-liquid metal located in the casting mould, or by a supplementary supply of electrically generated heat.

To ensure the correct dimensions of the casting, and to obviate deformation of the Vcasting moulds under the raised internal pressure, and to keep the moulds fluidtight, according to a further development of the invention the casting moulds employed for the process of the invention,

3,279,005 Patented Oct. 18, 1966 Mice before the production of the internal pressure, are subjected to an external pre-stressing pressure exceeding the internal pressure. This is advantageously elected by wedging against correspondingly strong casings and frames. This appropriate apparatus must be so constructed that it can be very quickly actuated.

According to a still further development of the invention the gas employed is argon gas, since this does not enter into any combination with metals or any other substance. On account of the high price of the gas it is preferably employed repeatedly. It is circulated through storage reservoirs and compression plants.

It is frequently of interest to determine in advance the speed of soliditication of the ingot, and it may also be of interest to let the solidication of the ingot proceed in a delinite direction, for instance only from the cylindrical periphery and from the core. This can be attained, according to yet another development of the invention, by coating the casting mould, at individual surfaces of the mould, with pieces of cast metal or other ireproof material. If for example moulded pieces of iireproof material are placed on the bottom of the mould, and also, after the filling of the mould, upon the upper surface of the liquid, hardly any cooling at al1 takes place from the bottom and from the t-op.

For carrying out the process, therefore, a pressure container without any mechanical devices for producing or increasing the internal pressure is preferably employed. This distinguishes the mould according to the invention from the more expensive moulds that are described in detail in the abovementioned publication in Stahl und Eisen.

Further details of the invention will be gathered from the following description, and from the accompanying drawings, in which:

FIGURE 1 shows a casting mould according to the invention in longitudinal sectional elevation;

FIGURE 2, a half Section on the une n n in FIG- URE 1;

FIGURE 3, a half-section on the line III-III in FIG- URE l; Y

FIGURE 4, a view of the casting mould after it has been clamped in a frame shown in section; and

FIGURE 5 is subdivided into detail FIGURES a to s illustrating the various positions which the appliances necessary for carrying out the process assume in succession.

According to FIGURE l, a bottom plate 1 is placed upon an under-plate 3 provided with wheels 2. The bottom plate has anrinner recess 4, into which a lling-piece 5 is inserted. The bottom plate also has a cylindrical recess 6, into which the' copper inner jacket 7 of the casting mould is placed. From FIGURES 2 and 3 the shape of the copper inner jacket 7 can be recognized. It has four positions 8 of quite small wall thickness. I'he recesses hereby arising in the jacket 7 are iilled up by wedges 9 of approximately triangular cross section. The inner jacket 7, which forms the core of the mould, is supported upon a core-stud 10, of steel. In it are inserted cooling elements 11, with bores for cooling water, which have a connection to a cooling-water pipe 12 in the under-plate 3, and open into the atmosphere at 1,3. The core 7 is externally cylindrical, but internally frusta-conical, the core stud 10 having a correspondingly frusto-conical shape. The outer wall of the casting mould is formed by a twopart copper wall 14, with butt joints 15. The copper wall is internally and externally cylindrical, and is supported against a two-part steel jacket 16, the parts of which meet one another -at the butt joint 17, the iianges 18 of which are held together 'by means of screw bolts 19. The steel jacket 16 is bolted to the bottom plate 1 at 50, and is provided with cooling elements 20, with bores for the cooling Water, which find a continuation in the ducts 21 of the bottom plate 1, and open into the atmosphere at 22. Through them, cooling water or wet steam can be admitted and exhausted. The outer wall surface of the two-part steel jacket 16v is conical, and is surrounded by an internally conical initial stressing ring 23, which, when it is pressed downwards, presses the steel mould parts 16 and the copper mould parts 14 together.

The mould is closed by a cover 24, which is placed, with a filling piece 25, upon the core jacket 7, and furthermore accommodates, in an annular groove 24a, the upper rim of the outer mould Wall 14, 16. A bore 26, with a coupling means 27, enables gas to be forced into the cavity of 'the mould. A bore 28, with an outlet valve 29, enables the most highly compressed gas to escape from the casting mould. By 30 is denoted a pressure gauge, and by 31 a safety valve, which opens the duct 31a as soon as the pressure in the casting mould exceeds a predetermined limit. An electrical heating means 32, which may be designed for instance as la heating coil, a hot Wire or lan arc for condenser discharge, has an electrical lead by way of a duct 33a at 33.

' The corners 34, each indicated black, denote packing rings or packing material. By 58 and 59 are denoted heatchecking plates, of ceramic material for instance.

The mem'bers 7 and 14 may consist of material other than copper, but it must be a good conductor of heat. To these parts is preferably applied a wear-proof film of freproof metal oxides. The core of the casting mould, consisting of the copper member 7 and the steel core-stud 10, is made so stout that it can take up the hydrostatic pressure of the liquid or solidifying metal, which corresponds to the rise of pressure of the high-pressure gas in the casting mould. Furthermore it must withstand the shrinkage pressure of the solidifying metal. The angles of the cones are in any case so selected that the parts that slip one upon another are self-checking.

The progress of the process according to the invention will now be describedwith reference to FIGURE 5, items a to s.

Upon the bottom plate 1, which rests upon the travelling under-plate 3, the core 7, 10 is -rst mounted, with I the aid of a crane, as shown in FIGURE a. Then the outer mould 14, 16 is mounted upon the bottom plate 1,

.as shown in FIGURE b. Next the conical prestressing ring 23 is slipped over the steel jacket 16, FIGURE c. Then theunder-plate 3 travels into a press 35, FIGURE d, by which the pre-stressing ring 23 is pushed down. Next, according to FIGURE e, the filling of the casting mould with an accurately measured quantity of metal is effected. As promptly as'possible after the completion of the pouring, the cover 24 is put on, FIGURE f. 'I'he travelling under-plate 3 now rolls into a frame 36, the

two frame members of which are held together below by a frame plate 37. The frame 36 stands upon a frame carriage 38, as shown in FIGURE 4 and in FIGURE g of FIGURE 5. The frame carriage 38 can travel so deeply in a recess 39 of the workshop oor 42 that rails 40 carried by it, on which the carriage 3 runs, are flush with rails 41 which lie on the workshop floor 42, so that the travelling yunder-plate 3 can be pushed straight away into the frame 36. In this position a press 43, suspended from the crane, travels into a position above the frame 36, and

presses a wedge 44 between the cover 24 and a co-acting l wedge 45, which is lixedly connected with the frame 36. The cover 24 is thereby firmly pressed on to the casting mould.

Argon gas from a bottle 46 is now passed through` the inlet valve 27 into the cavity between the plate 58 and p of heat from the melt or by the special electrical heating means mentioned above, and until the castmetal has solidified under this pressure. After the termination of this operation the argon gas is drawn olf and collected.

The frame carriage 38 travels on somewhat on the op-` travelling 'bottom plate 3 travels underneath a press 49 (FIGURE l), which pushes up the press ring 23 from below, while the steel jacket 16, with the copper jacket 14, are held from above.

According to FIGURE m the press ring 23 is lifted off the steel jacket 16, and is returned to the position shown in FIGURE c in readiness to be used again. Next it is important that the removal of the mould core 7, 10 is quickly effected, since this core should be subjectto the steadily increasing shrinkage stress of the cooling hollow cast material. In order to enable the core stud 10 to be removed, the outer jacket 16, with lthe bottom plate 1, which is bolted to it at 50 (FIGURE 1), is lifted (see FIGURE n) by a crane, and placed upon a discharge 'carriage 51, FIGURE o. The latter supports the-bottom plate 1, and has an inner cavity 52, into which the core stud 10, by a press 53, (FIGURE p), beneath which the `discharge carriage 51'is slid, is ejected in a downward direction. Here, of course, a supplementary supporting of the body of the discharge carriage 51 is necessary, to avoid crushing its wheels 54.

After the core-stud 10, according to FIGURE p, has been expelled downwards from the copper jacket 7, the latter no longer has a firm seat in the ingot, since it comprises the thin, flexible parts 8 (compare FIGURE 2); and the wedges 9, after the Withdrawal of the core-stud 10, immediately drop out of themselves. If the jacket 7, with the aid of the press 53, has been expelled downwards into the cavity 52 along with the core stud 10, the outer jacket 16 can ybe lifted by means of a crane, as shown in FIGURE q, with the bottom plate, follows it. According to FIGURE r, the mould core 10, 7 is then lifted out of the expulsion carriage 51. The outer jacket-14, 16, with thebottom plate 1, is now placed upon the under-plate 3 again. By means of `a spreader clamp 55, which engages in the internal cavity of the ingot, the ingot is drawn out of the mould 14, 16, as shown in FIGURE s. This is possible without difficulty, because meanwhile the lcasting has shrunk. All the parts are now ready for a fresh charge.

The time required for heating up the argon gas amounts in Vgeneral to only la few seconds. The duration ofthe soliditcation of an ingot of a length of 850 mm., an external diameter of 250 mm. and an internal vdiameter of mm., with a fall of temperature from l350 to about 1250 C., amounts however to from 60 to 80 seconds for example. By the abovementioned provision-of cool lining members 58 of metal or ceramic material, the time for the development of pressure, thatV is, for the heating of the argon gas, can be increased from 2 seconds, for example, to about 50 seconds.`

The cooling of the mould members is continued, pref` erably steadily, during the entire operation according vto FIGURE 5, items e to s, so that the mould members are` tinued at least until the solidified but still very hot casting met-a1 is removed from the mould. For uniform working it is obviously desirable that the argon gas according` to FIGURE 5, item g, should always be supplied at the same pressure. If the argon gas is stored in a battery of bottles, this aim is attained by interposing an ordinary pressure-reducing valve between the battery of bottles and the casting mold.

in which case the ingot, togetherl Iclaim:

1. A method for the solidilcation of metal under gaseous pressure in a casting mold, comprising the steps of: pouring the molten metal to be solidied into the casting mold, covering the molten metal in the casting mold with a thermally insulating layer, closing the mold, forcing inert gas under high pressure into the casting mold above the thermally insulating layer, and heating the inert gas in the casting mold by means of an electrically generated source of heat.

2. A method for the solidication of metal under gaseous pressure as claimed in claim 1, the electrically generated source of heat being an arc for condenser discharge.

3. A method for the solidication of metal under gaseous pressure as claimed in claim 1, the inert gas employed being argon.

References Cited by the Examiner UNITED STATES PATENTS Kelley 22-200 X Jensen 22-72 Ling 22-72 Mullaney et al 22214 X Poudevigne 22-72 X Kozinski 22-200 Operhall et al. 22-200 J. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner. 

1. A METHOD FOR THE SOLIDIFICATION OF METAL UNDER GASEOUS PRESSURE IN A CASTING MOLD, COMPRISING THE STEPS OF: POURING THE MOLTEN METAL TO BE SOLIDIFIED INTO THE CASTING MOLD, CONVERING THE MOLTEN METAL IN THE CASTING MOLD WITH THERMALLY INSULATING LAYER, CLOSING THE MOLD, FORCING INERT GAS UNDER HIGH PRESSURE INTO THE CASTING MOLD ABOVE THE THERMALLY INSULATING LAYER, AND HEATING THE INERT GAS IN THE CASTING MOLD BY MEANS OF AN ELECTRICALLY GENERATED SOURCE OF HEAT. 